1. Field of the Invention
The present invention relates to a fuse circuit including fuses that can be cut by laser or the like, and a semiconductor integrated circuit device including the fuse circuit.
2. Description of the Related Art
A fuse circuit that can be cut by laser has been widely used for a semiconductor integrated circuit device for the purpose of characteristics adjustment or function switching. For example, in a bandgap reference voltage generation circuit, in order to correct reference voltage temperature characteristics caused by manufacturing fluctuations to obtain a high accuracy reference voltage, a fuse is cut by laser to turn on or off a switch connected to a resistor, thereby adjusting a resistance value.
FIG. 7 is a circuit diagram of a related-art fuse circuit. The related-art fuse circuit includes a resistor R1, a fuse H1, a fuse H2, and a resistor R2 that are connected in series between power supply terminals. A terminal A of the fuse circuit is connected to a switch circuit that is connected in parallel or in series to one of resistors in a bandgap reference voltage generation circuit, for example. When the terminal A becomes “High” level or “Low” level, the switch circuit is turned on or off to adjust a resistance value of the resistor in the bandgap reference voltage generation circuit, thereby adjusting reference voltage temperature characteristics. The level of the terminal A is determined by which of the fuse H1 and the fuse H2 is cut by laser. Which of the fuses is to be cut is determined after the reference voltage is measured in a stage before adjustment, that is, in a state in which none of the fuses is cut. Because a material with high conductivity is used for the fuse in general, in consideration of the area of a chip, the resistor R1 and the resistor R2 are connected for the purpose of limiting a current that flows between the power supply terminals in the state in which the fuses are not cut.
As described above, by mounting the fuse circuit that can be cut by laser on a semiconductor integrated circuit device, added value of high accuracy is realized in a bandgap reference voltage generation circuit, for example.
In recent years, however, semiconductor integrated circuit devices have been strongly required to be high in accuracy and high in performance and more strongly required to be low in cost. The cost of the semiconductor integrated circuit device is affected by the chip size, and it has therefore been required to reduce the chip size as much as possible.
In other words, the circuit has been strongly required to have as simple a configuration as possible. In such circumstances, the related-art fuse circuit as described above has a problem in that the chip size increases with an increase in adjustment parts and the cost increases.